Large scale mechanical power presses are used in a wide range of industries to perform an equally wide range of tasks. For example, in the automotive industry power presses are often used to stamp steel or sheet metal into relatively small car parts such as engine struts as well as significantly larger vehicle body components such as deck lids, doors, and quarter panels. Depending upon the application, these power presses can be designed to generate forces of 4000 tons or more. Thus, while mechanical power presses are extremely useful industrial tools, the large forces they generate create a potential for severe physical injury to operators and maintenance personnel.
There are many instances in which operating or maintenance personnel could potentially be placed at risk. For example, due to the tremendous forces and impacts involved in the operation of these mechanical power presses, the dies carried by the presses experience considerable stress and must be subjected to periodic maintenance procedures. Some of the more extensive maintenance procedures such as re-grinding require the removal of the dies from the press. Thus, the press presents little danger to personnel during these procedures. However, more minor maintenance procedures such as removing minor blemishes from the dies involve on-press adjustments which often require maintenance personnel to place portions of their bodies between the dies of the press. On-press maintenance operations such as these thus present considerable safety concerns. Should a power press accidentally cycle to the closed position while being serviced by maintenance personnel, an unfortunate individual caught within the press could easily suffer death or dismemberment.
The realities of press operation in an industrial setting, thus, present an operator with competing concerns. On the one hand, an operator must minimize the down time of a given press by performing maintenance procedures as quickly and efficiently as possible. On the other hand, the operator must not be subjected to undue risk while performing these maintenance procedures.
In the past, power press designers have addressed these competing concerns by providing power presses with safety blocks which, through the use of attached plugs, shut the press down when they are removed from their storage compartments. These safety blocks must be manually positioned between the upper and the lower halves of the die to prevent the slide from inadvertently moving to its closed position due to a sudden loss of brake or counterbalance, or a break in the connection between the slide and the drive. While these safety blocks are effective in preventing accidental injury when properly employed, operators and maintenance personnel unfortunately sometimes forget or choose to forego using them when working on the press or dies. Thus, the overall effectiveness of these safety blocks is reduced by human error and carelessness.
In addition, since safety blocks typically have a fixed length, they can only be used to fix the position of a press slide at a specific height. However, some maintenance procedures are more easily performed with the press stopped at different points in its cycle (i.e. with the slide stopped at different heights in the stroke). Since power presses are typically provided with a single set of safety blocks having a single fixed length, maintenance personnel must choose between performing certain maintenance procedures with the slide secured by the safety blocks at a height which is improper for that given procedure, and foregoing the use of the blocks altogether while performing that procedure with the slide adjusted to a convenient height.
While it is not known that any prior inventor had locked a power press gear train in accordance with the present invention, a prior art device for locking the gear train of a transfer feed mechanism used to transfer work pieces into the work area of a transfer feed press is illustrated in FIG. 13. As illustrated in FIG. 13, this prior art locking device operated similarly to the instant gear train locking mechanism for mechanical power presses. However, since the prior art locking mechanism was used to prevent a transfer feed mechanism from moving rather than to lock the gears of a mechanical power press, it employed substantially smaller mechanical jacks than the instant invention (10 and 20 ton jacks as compared to 50 and 150 ton jacks on the present invention). In addition, unlike the instant invention, the prior art locking mechanism did not include an idler gear but instead selectively meshed directly with the gears of the transfer feed mechanism as illustrated in FIG. 13.